Method of treating acne

ABSTRACT

A method of selectively enhancing photothermal sebaceous gland disruption and treatment of acne is disclosed. The method provides for alleviation of the acne symptoms as well as preventing acne recurrence and new acne from occurring.

RELATED U.S. APPLICATION(S)

This application claims priority from U.S. patent application Ser. No.09/924,156, filed Aug. 7, 2001, which is hereby incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate in general to the combineduse of laser therapy and laser light absorbing agents in the treatmentof skin conditions associated with the production of sebum by sebaceousglands. More particularly, embodiments of the present invention relateto methods of preventing, reducing, eliminating, or otherwise treatingunwanted skin conditions, such as acne, using laser light and one ormore exogenous chromophores to disrupt production of sebum withoutsignificant harm to surrounding normal tissue.

2. Description of Related Art

Unwanted skin conditions associated with the production oroverproduction of sebum are well known. One example of such an unwantedskin condition includes common acne which is a major treatment concernof many dermatologists. It is estimated that as many as 32 millionAmericans exhibit some form of unwanted acne.

The treatment of acne is of major concern to dermatologists. Acneaccounts for more than four million visits to dermatologists each year.Typically, acne arises in the early teen years and subsides by the midtwenties. In many cases, particularly in women, acne remains a chronicproblem well into the adult years. It is estimated that as many as 32million Americans suffer from acne.

Acne vulgaris, the most common form of acne, is the result of thesecretion of sebum by the sebaceous gland into a blocked pore. Continuedsecretion results in buildup of the sebum in the blocked pore. Bacteriain the pore gives rise to infection and a common unsightly skincondition known as pimples. Sebaceous gland hyperplasia is also a commonform of acne in which the sebaceous gland grows or become enlarged as aresult of overproduction of sebum. A pimple is formed even if the glandis not blocked.

Sebaceous glands and the sebum they produce apparently have no commonlyaccepted significant function in humans. The skin of young children doesnot appear to be negatively affected by the almost total lack of sebum.The only known role of sebum in humans is in the pathogenesis of acne.In the past, physicians treated acne with radiation therapy to destroythe sebaceous gland. Radiation, however, does not specifically targetthe sebaceous glands, and can cause significant morbidity to normaltissue because of its mutagenic toxicity. Increased risk of cutaneouscarcinoma has also been associated with radiation therapy. Current acnetreatments do not eradicate the sebaceous glands selectively and withoutharm to surrounding normal tissue, and therefore remain non-curative andinadequate. The result is years of chronic therapy and potentialscarring for the patient.

Selective photothermolysis is a method of causing selective andirreversible photothermal damage to tissue structures containing achromophore that can be used to distinguish that target structure fromsurrounding tissue. For a light source, typically a laser, to be usefulfor selective photothermolysis, it must emit with sufficient intensityat a wavelength preferentially absorbed by the target chromophore. Thepulse duration or exposure time of the source must be less than thethermal relaxation time of the target to minimize temperature increasesin tissue surrounding the target. Techniques based on this concept usingwell known laser systems are well established for treatment of benigncutaneous vascular lesions such as portwine stain (PWS), birthmarks,telangiectasias, hemangiomas, warts, psoriasis, arthritis in whichhemoglobin in the abnormal ectatic lesional vasculature serves as thechromophore and the target is the vessel wall, as well as,atherosclerotic plaque and other desired applications. See U.S. Pat. No.5,312,395; U.S. Pat. No. 5,749,868; U.S. Pat. No. 5,257,970; U.S. Pat.No. 5,066,293, U.S. Pat. No. 5,346,488, “Selective Photothermolysis:Precise Microsurgery by Selective Absorption of Pulsed Radiation”,Anderson et al., Science, 220:524-527 (1983); Spears et al. J. Clin.Invest, 71, 39-399 (1983), the disclosure of each of which is herebyincorporated by reference in their entireties for all purposes. Thedeepest blood vessels contributing to the color of PWS lesions areapproximately 1 mm below the skin surface, and are accessible toselective photothermal targeting using available lasers such as the 585nm pulsed dye laser. The theoretical advantages of selectivephotothermolysis have been borne out in clinical studies showing thatPDL (pulsed dye laser) treatment of benign cutaneous vascular lesions isassociated with very low risk of scarring. However, photothermolysistechniques involving the direction of laser light onto the surface ofskin would be more effective if the laser light was not substantiallyabsorbed by components of skin and particularly if an exogenouschromophore was used which selectively collected in the targeted tissueand which absorbed laser light at a wavelength substantially outsidethat absorbed by normal skin components.

One approach to the treatment of acne is to reduce the production ofsebum by disrupting or even destroying the sebaceous gland. One suchmethod described in U.S. Pat. No. 5,817,089 includes forcing, forexample by the use of ultrasound, an exogenous chromophore into spaceswithin or adjacent sebaceous glands. The chromophore is then illuminatedwith short pulses of laser light so as to provide sufficient energy tothe chromophore to create explosions which blow off layers of dead skincells and/or destroy tissue responsible for hair growth and/or sebumproduction.

The use of beta-carotene as an exogenous chromophore along with lasersto treat acne is considered in U.S. Pat. No. 5,304,170. However, thelaser light has a wavelength between 425 nm and 550 nm which suffersfrom poor penetration within the tissues. Further, while beta-carotenedoes collect in sebaceous glands, it also collects in the tissue betweenthe glands and surrounding tissue and skin components, resulting in poorselectivity and yellowing of the skin.

Efforts to use lasers to treat certain skin conditions and to effecthair removal include Manuskiatti et al., J. Am. Acad. Dermatol., vol.41, Number 2, Part 1, pp. 176-180 (1999), Friedlander, PediatricDermatology, vol. 15, No. 5, pp. 396-398 (1998), Shuster, ActaDermatovener (Stockh) Suppl., 120, pp. 43-46, Sigurdsson et al.,Dermatology, 194, pp. 256-260 (1997), Sumian et al., J. Am. Acad.Dermatol., Vol. 41, Number 2, Part 1, pp. 172-175 (1999), the disclosureof each of which is hereby incorporated by reference in their entiretiesfor all purposes. However, these efforts do not recognize the use oflaser light having a wavelength outside that significantly absorbed byskin or skin components or the use of an exogenous chromophore which canbe selectively introduced to sebaceous glands.

Accordingly, there is a need in the art to provide methods of treatingunwanted skin conditions associated with sebum production oroverproduction which employ laser light having a wavelength outside thatsubstantially absorbed by skin or skin components. There is also afurther need in the art to selectively localize the effects ofphotothermolysis to sebaceous glands using a chromophore which absorbslaser light having a wavelength outside that substantially absorbed byskin or skin components and further without significantly harmingsurrounding normal tissue. There is a further need to develop methodsfor introducing an exogenous chromophore into sebaceous glands wheresuch chromophore would normally lack affinity for sebaceous glandmaterial.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention are directed to methods in humanswhich are useful in treating skin conditions associated with theproduction or overproduction of sebum by sebaceous glands. Sebaceousglands are treated according to one method of the present invention in amanner to reduce or prevent the production of sebum withoutsignificantly harming or otherwise adversely affecting surroundingnormal tissue. Methods of the present invention also include treatingunwanted skin conditions associated with sebum production, such as acne.According to the present invention, the production of sebum is reducedin a manner to reduce, prevent or eliminate the occurrence orreoccurrence of unwanted skin conditions, such as acne.

According to one embodiment of the present invention, a chromophore,such as a dye, is administered to the site of irradiation. The term“chromophore” also includes compounds having chromophoric groups such asnitro groups, azo, alkylene units, esters, carbonyl groups, aldehydes,alkynes, aromatic rings, heterocyclics, carboxylic acids and the like.The chromophore acts to selectively absorb the chosen wavelength oflaser light thereby enhancing the effectiveness of the irradiation.Other chromophores or photoactive or photoabsorbable compounds can beused which themselves act as therapeutic or cytotoxic agents uponirradiation. According to the methods of the present invention, anexogenous chromophore is selectively introduced into a holocrine gland,such as a sebaceous gland, selected for treatment. The exogenouschromophore preferably absorbs laser light having a wavelengthsignificantly outside the wavelengths absorbed by skin or skincomponents. According to one embodiment, an otherwise lipophobicexogenous chromophore is rendered substantially lipophilic so as to beselectively introduced into sebaceous glands. The sebaceous glandshaving the chromophores introduced therein are then irradiated withlaser light having a wavelength, duration, fluence and spot sizeselected to preferentially heat the sebaceous glands in a manner todisrupt, reduce, eliminate or otherwise interfere with the production ofsebum. According to one embodiment, the sebaceous glands are heated tothe point of denaturation and to effectively prevent the production ofsebum that is required for the development or continued presence ofunwanted skin conditions such as acne.

Other features and advantages of certain embodiments of the presentinvention will become more fully apparent from the following descriptiontaken in conjunction with the accompanying figures and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the course of the detailed description of certain preferredembodiments to follow, reference will be made to the attached figures,in which,

FIG. 1 is a photomicrograph showing tissue containing sebaceous glandsviewed under normal illumination with white light wherein the tissue hasbeen treated with a topical administration of indocyanine green whichhas been rendered lipophilic.

FIG. 2 is a photomicrograph of the same tissue shown in FIG. 1 butilluminated at 810 nm and observed through an 840 nm bandpass filter.FIG. 2 shows that indocyanine green is present in the sebaceous glandsbut not in the tissue between the glands.

FIG. 3 is a sample of human skin treated with an indocyanine greenmicroemulsion for 24 hours before excision.

FIGS. 4A and 4B are histological studies from a human volunteer withactive acne.

FIGS. 5A-5D are photographs showing a reduction in acne after treatmentusing the invention described here.

DETAILED DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS

The principles of the present invention may be applied with particularadvantage to treat unwanted skin conditions or disorders associated withthe production or overproduction of sebum by sebaceous glands. Accordingto the teachings of the present invention, sebaceous glands or othercomponents of the pilosebaceous unit such as the infundibulum openingare altered, modified or disrupted by selectively introducing one ormore exogenous agents, dyes or chromophores to the sebaceous glands inthe affected area of skin to enhance the absorption of laser light at asite of irradiation within the skin and to also aid in the selectiveabsorption of laser light. Exogenous chromophores or compounds includingchromophoric groups are administered to take advantage of the deepertissue penetration of longer visible or near-infrared wavelengths. Oneor more photoactivated compounds can also be administered as necessaryto therapeutically treat the affected area of the skin. The amount,duration and mode of administration of the chromophore or otherphotoactive agent will depend on its properties and the makeup of theindividual on which the treatment is to be carried out.

The affected area of skin is then irradiated with light having awavelength strongly absorbed by the chromophore. The light has awavelength, duration, fluence, and spot size sufficient to result inheating of the chromophore in the sebaceous glands such that thesebaceous glands are modified, altered, destroyed, damaged, disrupted orotherwise rendered incapable of producing sebum at excessive or normallevels. According to one embodiment, the sebaceous glands are preventedfrom producing sebum necessary to promote or sustain unwanted skinconditions such as acne. In other embodiments, the sebaceous glands maybe disrupted to alleviate symptoms of medical conditions other thanacne, e.g. seborrheic dermatitis commonly seen in infants and in HIVpatients.

In one embodiment, the laser light is produced by a tunable pulsed dyelaser system or diode laser system and is characterized as having awavelength corresponding to that which is absorbed by the selectedchromophore. Preferably, the laser light also has a wavelength that issubstantially transmitted by the outer layers of the skin, i.e., thefirst 1 to 2 millimeters of skin. “Substantially transmitted” is usedherein to indicate that not less than 60% of the laser light istransmitted through the first 2 millimeters of skin, or alternatively,not less than 60% of the laser light reaches target sebaceous glands. Ingeneral, suitable pulsed dye laser systems useful in the presentinvention include a power source, a flashlamp capable of emittingmultiple pulses of light, a dye reservoir containing a dye suitable forstimulated emission of light, and an optical resonator having an outputcoupler. The power source, flashlamp, dye reservoir and opticalresonator are operatively connected so as to generate multiple pulses oflaser light having a defined wavelength and pulse duration. An opticalfiber is optically coupled to the optical resonator in a manner to allowthe multiple pulses of laser light to travel from the optical resonatorthrough the optical fiber to the tissue area to be irradiated with adefined pulse fluence. A handpiece delivery system incorporating theterminal end of the optical fiber is used to effectively direct thelaser light source to the target area.

In a second embodiment, light is produced by a tunable dye system thatemits light continuously. That is, light is emitted continuously fromthe source. Preferably, the light has a wavelength that is substantiallytransmitted by the outer layers of skin. Suitable light system have alight source, such as an arc lamp, a dye reservoir for selecting thewavelength of light emitted from the system, a monochromator, and one ormore shutters to prevent passage of the light. The shutter can be openedand closed using a pre-selected delay time to provide for pulsing of thelight. For example, the shutter can be opened for about 1 ms and thenclosed for about 1 second to provide for a pulse duration of about 1 mswith a delay time of about 1 second. An optical fiber is opticallycoupled to the light system in a manner to allow the multiple pulses oflight to travel from the optical resonator through the optical fiber tothe tissue area to be irradiated with a defined pulse fluence. Ahandpiece delivery system incorporating the terminal end of the opticalfiber is used to effectively direct the light source to the target area.

According to one embodiment, useful wavelengths are between about 700 nmand about 1200 nm, preferably between about 750 nm and about 850 nm andmore preferably between about 800 nm and about 820 nm. 810 nm is aparticularly preferable wavelength since melanin, the primary human skinpigment, does not absorb strongly at that wavelength. Additionally,commonly used topical acne treatments, such as Retin-A®(all-trans-retinoic acid), typically absorb light at about 351 nm. Thus,acne patients may undergo the treatment methods described here whilecontinuing with other topical acne treatments. The laser light has apulse duration less than the thermal relaxation time of the volume oftissue being irradiated. Specific pulse durations include between 0.1msec and about 500 msec, preferably between about 1 msec and about 200msec. The delivered fluence of the pulsed laser light is between about 1J/cm² and about 50 J/cm², preferably between about 5 J/cm² and about 40J/cm² and more preferably about 10 J/cm². The irradiated spot size issufficient to include the manifestation of the unwanted skin conditionof interest as a whole or portions thereof. According to an additionalembodiment, the spot size is sufficient to include not only the acne,but also an area of normal tissue adjacent to or surrounding the acne tobe treated which may include sebaceous glands which have not yetdeveloped into visible acne, e.g. preferentially the entire holocrinegland and surrounding tissue including other sebaceous glands aretreated. The area of visibly normal tissue adjacent to or surroundingthe acne to be treated is referred to herein as the “margin” or “marginof tissue.” Alternatively, the laser light has a spot size sufficient toirradiate only the margin or portions thereof, or part of the margin andpart of the acne. Spot sizes in accordance with the present inventioninclude those between about 1 mm to about 20 mm, preferably about 5 mmto about 15 mm. Depending upon the intended use and the size of thesubject's sebaceous glands, the spot size may be smaller, e.g. about 500μm to about 1 mm for use in infants, or larger, e.g. about 20 mm toabout 30 mm for use in adults having larger sebaceous glands. Inpreferred embodiments, the spot size may be reduced during use byadjustment of the optical fiber aperture, e.g. the spot size can beincreased or decreased during use.

According to the present invention, the area of the individual to betreated should be irradiated at least once with laser light having theabove parameters, with the appropriate number of pulses necessary totreat the entire area. The complete treatment may be repeated up to fivetimes with at least one week between each treatment.

It is to be understood that other lasers, such as yellow, green and bluewavelength lasers which produce laser light suitable of being absorbedby an exogenous chromophore taken up by or otherwise introduced intosebaceous glands, are useful within the scope of the present inventionand include Argon ion lasers, Copper-vapor lasers, alexandrite lasers,ruby lasers, semiconductor diode lasers, frequency-doubled Nd:YAGlasers, and other dye lasers pumped by a Nitrogen laser or Argon-ionlaser and the like. The lasers and other light sources within the scopeof the present invention are preferably pulsed but may also operate in acontinuous-wave (cw) mode with a scanner to automatically scan thetreatment area and provide temporal modulation of the laser intensity onthe treatment site.

The advantage of the selective photothermal sebaceous gland targetingover conventional methods of disrupting sebaceous gland activity includethe more efficient use of laser light should a chromophore be used thatabsorbs at a wavelength substantially transmitted by skin or skincomponents. In addition, such a chromophore when rendered substantiallylipophilic provides selective loading of the chromophore into thesebaceous glands versus surrounding tissue. This allows for a method ofdiscriminating between sebaceous glands as opposed to surrounding tissuefor purposes of absorption of laser light.

According to the invention, the sebaceous glands are irradiated to theextent to cause irreversible damage to the sebaceous glands but also ina manner to spare surrounding tissue, e.g. the thermal damage tosurrounding tissue is minimal. This method is implemented, depending onthe area of skin to be treated, by means of the pulsed dye laser or anyother source of radiation preferentially absorbed by the exogenouschromophore selectively introduced into sebaceous glands.

According to additional embodiments, the methods described here may beused to treat skin conditions other than acne. For example, lipophilicchromophores may be administered or disposed on skin lesions. Becausethe rate of uptake of compounds by certain skin lesions may be largerthan the rate of uptake in normal tissue, the skin lesions may beselectively destroyed using the methods described here. That is, theconcentration of chromophores inside the skin lesion cells typically canbe much larger than the concentration inside normal cellular tissue.Therefore, administration of light to the region of the skin lesions,destroys the skin lesions while minimizing the amount of normal tissuesurrounding the skin lesions that is destroyed. Alternatively, the skinlesion can be injected with a chromophore prior to irradiation of theskin lesion.

The following examples are set forth as representative of the presentinvention. These examples are not to be construed as limiting the scopeof the invention as these and other equivalent embodiments will becomeapparent in view of the present disclosure, figures and accompanyingclaims.

EXAMPLE I Introduction of a Chromophore to Sebaceous Glands

The selective introduction of a chromophore to sebaceous glands isaccomplished by topically applying a selected chromophore to the skinunder conditions that permit the chromophore to selectively localize tothe sebaceous glands. The selective introduction of a chromophore tosebaceous glands is most readily accomplished using lipophilicchromophores, or alternatively, by preparing less lipophilicchromophores in a carrier that renders them more lipophilic.

Chromophores useful in the methods of the invention should meet at leastthe following criteria. First, chromophores of use in the methods of theinvention must strongly absorb light at a selected wavelength or portionof the spectrum. There are a large number of chromophores known in theart that meet this criterion, but particularly preferred among them arethose that strongly absorb light energy at a wavelength or portion ofthe spectrum that is not strongly absorbed by natural skin pigments suchas melanin, which absorbs at between about 500 nm to 600 nm.

A second criterion for a chromophore useful in the methods of theinvention is that it be lipophilic, i.e., substantially soluble in a fator lipid. The lipophilic nature of the chromophore facilitates theselective introduction of the chromophore to the sebaceous gland.Lipophilic chromophores include, for example, organic tissue stains andbeta-carotene. Lipophilic chromophores may be dissolved in an acceptableoil and then applied directly to the area of skin one wishes to treat.Alternatively, the pores of the skin may be opened using heat, steam andthe like to facilitate entry of the chomophores into the sebaceousglands.

It is recognized herein that a number of chromophores that absorb lightenergy at a wavelength or portion of the spectrum that is not absorbedby natural skin pigments, and thus might be expected to be useful forthe methods of the invention, are not lipophilic. That is, there are anumber of chromophores, particularly organic dye molecules, that wouldbe useful in the methods of the invention except that they are notsoluble in lipid or fat. Such chromophores include indocyanine green,methylene blue and other common dyes such as Rhodamine B and cresylviolet and the like. See also other chromophores useful in the presentinvention identified in U.S. Pat. No. 4,651,739, the disclosure of whichis hereby incorporated by reference in its entirety for all purposes.The methods of the invention overcome this limitation by combining suchchromophores with a lipophilic carrier preparation. In this way, thenon-lipophilic chromophores are rendered lipophilic, allowing theirselective introduction to the sebaceous gland.

Finally, a chromophore useful in the methods of the invention must besafe to apply to human skin. The chromophore must not be toxic orcarcinogenic in the amounts to be applied. Data regarding toxicity andcarcinogenicity of chemical compounds are widely known in the art.

EXAMPLE II Rendering Non-Lipophilic Chromophores Lipophilic

According to one aspect of the present invention, non-lipophilicchromophores, for example, indocyanine green, are rendered lipophilic byseveral possible methods, including the use of liposomes and lipidsuspensions. By associating a non-lipophilic chromophore with a lipid ineither a liposome or a lipid suspension, the chromophore is selectivelydeposited within the sebaceous glands.

Liposomes containing a non-lipophilic chromophore are prepared using thefollowing protocol. Appropriate amounts of the lipids are mixed in abeaker and melted at 75° C. The melt is then drawn into a syringepreheated in a water-bath at 75° C. A second syringe containing 0.05 Misotonic HEPES buffer, pH 7.4, is preheated to 70° C. The two syringesare then connected via a 3-way Teflon or metal stopcock. The aqueousbuffer is then injected into the lipid phase syringe. The mixture ismixed back and forth between the two syringes rapidly several timeswhile being cooled under cold tap water. This process is continued untilthe mixture is at room temperature. The resulting liposomal suspensionsare then examined using a light microscope to assure integrity andquality of the liposomal preparations. A non-lipophilic chromophore mayalternatively be prepared in a lipid suspension to facilitate selectiveintroduction of the chromophore to sebaceous glands. Specifically, achromophore may be placed in a lipid suspension by mixing an oil, achromophore, which has been previously dissolved in a small amount(relative to the amount of oil) of water or alcohol, and one or moresurfactants. Following vigorous stirring or shaking, the chromophore,dissolved in small water droplets, is suspended as an emulsion in thelipid. Following topical application, the suspended chromophore is thencarried to the sebaceous glands due to its close association with thelipid.

The exact makeup of the lipid chromophore suspension may vary, and caninclude at least one pharmaceutically acceptable oil, at least onesurfactant, and at least one chromophore dissolved in water or alcohol.Pharmaceutically acceptable oils for use in preparing lipid chromophoresuspensions include, but are not limited to olive oil, sesame oil, cornoil, and safflower oil. Alternatively, the chromophore may besolubilized in one or more liquid vitamins, such as a tocopherol(Vitamin E), to provide for delivery of the chromophore and to promoteepidermal health and maintenance.

As a general guideline, the ratio of oil to dissolved chromophoresolution used to prepare a lipid chromophore suspension should be atleast about 5:1, about 10:1, about 20:1, about 50:1, about 100:1, oreven as high as 200:1 or more by volume. The chromophore is preferably,but not necessarily, dissolved in water or an alcohol acceptable forhuman topical administration at a concentration close to the limit ofsolubility for that chromophore. A preferred method of delivering ICG tothe sebaceous gland would be a lotion with liposome-encapsulated ICG.The absorption and fluorescence characteristics of such lotion must beknown to properly design the in vitro and in vivo experiments. A lipidsuspension of ICG was prepared using the following protocol. 6 mg of ICGwere dissolved in 20 g of water. 3 g of the solution were mixed with 9 gTween 80, 15 g Span 80 and 23 g olive oil. The mixture was shaken for 1min and left to settle for 3 days. The resulting solution is a uniformtransparent liquid with negligible scattering. An identical clear lipidmix was prepared without dissolving ICG in water.

In this way, the concentration of the chromophore is kept as high aspossible after mixing with surfactant and oil. Alcohols acceptable fortopical administration include, but are not limited to ethanol,isopropanol and the like.

Surfactants useful in preparing lipid chromophore suspensions include,but are not limited to Tween 80 and Span 80. Generally, the surfactantcomprises from 0.1% to 70% (w/v) of the lipid chromophore suspension.The amount may be varied depending primarily upon the amount and type ofoil used and on the ratio of oil to dissolved chromophore solution used.Generally, the amount (mass or volume) of surfactant required varies indirect proportion to the volume of dissolved chromophore solution used;the greater the volume of chromophore dissolved in water or alcohol, thegreater the proportion of surfactant necessary to maintain the lipidchromophore suspension.

The amount of chromophore added to a lipid chromophore suspension canvary from about 0.01% to about 25% by weight of the entire lipidchromophore suspension. The amount of chromophore used is determinedempirically, using, for example, varied proportions of chromophore inlipid suspensions applied to the skin of an animal, followed bymicroscopic inspection to evaluate the density of chromophore localizedin the sebaceous glands. Generally, the better a chromophore suspensionlocalizes to sebaceous glands, the lower the relative proportion ofchromophore necessary in the lipid chromophore suspension.

A specific lipid chromophore suspension was prepared as follows. 15 mgof ICG powder was dissolved in 1 g (1 ml) of water, followed by theaddition of 3 g of Tween 80, 5 g of Span 80, and 7.667 g of olive oil.The suspension was vigorously shaken in a covered 50 ml tube for 5minutes. The absorption coefficient for the resulting lipid chromophoresuspension was measured and was typically between 350 cm⁻¹ and 690 cm⁻¹.

EXAMPLE III Selective Introduction of a Chromophore to Sebaceous Glands

The manner in which a chromophore is selectively introduced to sebaceousglands depends upon whether the chromophore is lipophilic ornon-lipophilic. A lipophilic chromophore is dissolved in apharmaceutically acceptable oil and applied directly to the area of skinone wishes to treat. A lipophilic chromophore is dissolved in oil at afinal concentration from about 0.001% to about 20% (w/v), with theproportion determined empirically using an animal model (e.g., thehamster ear model described herein or other appropriate model for humanskin as known in the art).

A non-lipophilic chromophore is applied as chromophore-bearing liposomesor as a lipid chromophore suspension prepared as described herein.Following application of either a lipophilic chromophore in oil,chromophore-bearing liposomes or a lipid chromophore suspension, eitherby swabbing, for example with a cotton swab, a cotton ball or a paintbrush, or by spraying or pouring the chromophore-oil mixture on the areato be treated, the mixture may be manually rubbed into the affected areato enhance the degree and/or rate of penetration of the mixture into thesebaceous glands. Generally, the mixture is contacted with the skin forabout 2 minutes to about 24 hours prior to irradiation. The time ofcontact of the mixture and the concentration of chromophore applied isdetermined empirically using an animal model for a given chromophorepreparation. The mixture may be applied to an entire area, for example,the face, or to a smaller portion of the area (e.g., a small portion ofthe face or back) one ultimately wishes to treat.

A chromophore is considered “selectively introduced” to sebaceous glandsaccording to the invention if greater than or equal to about 90% of thechromophore remaining associated with the skin after removal of excesschromophore preparation from the skin surface is observed in sebaceousglands. The proportion of a particular chromophore localized tosebaceous glands from a particular chromophore preparation (e.g.,chromophore in oil or chromophore in liposomes or lipid suspension) isdetermined using an appropriate animal model, such as the hamster earmodel described herein. Hamsters are known to have sebaceous glands intheir ears. These glands are typically on the order of 200 μm indiameter, making them somewhat larger than typical sebaceous glands inhumans. Nonetheless, the hamster ear is a convenient and instructivemodel for human skin and sebaceous glands.

For example, the non-lipophilic chromophore indocyanine green wasintroduced to sebaceous glands present in skin of the hamster earaccording to the following method. The lipid chromophore suspension wastopically applied to hamster ears and allowed to travel into the poresand sebaceous glands for 24 hours. After this time, the hamsters wereeuthanized and their ears were examined for evidence of ICG in thesebaceous glands. FIG. 1 shows a photomicrograph of skin from a hamsterear treated with ICG, illuminated under white light, and FIG. 2 showsthe same region illuminated under 810 nm light and observed through an840 nm bandpass filter. ICG fluorescence (840 nm) is stimulated byirradiation with 810 nm light. Both the white light and fluorescencemicrographs of the treated region show the chromophore is primarilylocalized to the sebaceous glands. Experimentally, it is estimated thatapproximately 5% of sebaceous gland lipid is ICG lipid.

Another method for evaluation of the ICG uptake is based on the use ofSebutape® adhesive patches commercially available from CuDerm Corp.(Dallas, Tex.). The patch consists of a microporous film acting as apassive collector of sebum. After the application of the ICGmicroemulsion and cleaning of the skin, a Sebutape® patch will beapplied to the skin and analyzed for fluorescence. The lipid ICGmicroemulsion, if present on the skin surface, would penetrate into thepatch and the patch would fluoresce under illumination with 810 nmlight. The skin will be cleaned and a new patch will be applied untilthere is no fluorescence from the patch, thus indicating that the skinsurface is clean from ICG. A fresh patch will be applied to the cleanskin surface and kept there for an hour. After an hour on the skin, thatpatch will be examined for sebum collection and fluorescence. If thepatch were applied to a skin site without active sebaceous glands therewould be no sebum collected in the patch and thus no fluorescence. Ifthe patch collects sebum, but there is no fluorescence, the ICGmicroemulsion did not penetrate in the sebum contained in the sebaceousgland. Such result would indicate that the application procedure for theICG microemulsion has to be improved, e.g. it has to be applied for alonger time. If the patch collects sebum and there is fluorescence, thesebaceous glands are successfully loaded with ICG and they can betreated with the laser. The intensity of the fluorescence signal can berelated to the ICG concentration in the sebum and the treatment fluencecan be adjusted accordingly.

Another method for evaluation of the ICG uptake is with an appropriateimaging system. This imaging system will incorporate a monochrome CCDcamera with a removable band-pass filter designed to selectively detectthe ICG fluorescence. It will also incorporate various objectives toallow either large field, low resolution imaging or narrow field, higherresolution imaging. The camera will be connected to a frame grabber in acomputer in order to digitally record the images and perform imagetreatment. It would be possible to identify the ICG loaded sebaceousglands and hair follicles on the fluorescence image. In addition, it ispossible that the fluorescence image would reveal a residual layer ofICG microemulsion on the skin surface. Such layer would have adeteriorating effect on the penetration ability of the laser during thetreatment and would contribute to unnecessary heating of the epidermis.The presence of such residual layer would indicate that the skincleaning procedure would have to be repeated. The intensity of thefluorescence signal from the sebaceous glands can be related to the ICGconcentration in the sebum and the treatment fluence can be adjustedaccordingly.

Selective delivery of ICG in the sebaceous glands in human skin using abiopsy sample was performed. For this study, an eligible patient wasscheduled to have some undesirable skin lesions surgically excised. Theday before the surgery, an ICG-containing lipid solution was applied tothe margin area of the skin that is normally excised around the skinlesion. After the surgical excision of the lesion and the margin area,the margin area was sent for fluorescence analysis. The samples ofexcised marginal skin were sectioned as thin slices and mounted onmicroscope slides. FIG. 3 shows the images obtained from such samplewith normal light (left panels) and with a fluorescence band-pass filterunder illumination with the 810 nm diode laser (right panels). Thedashed arrow points to a pilosebaceous unit with attached sebaceousgland.

The fluorescence photographs confirm the selective delivery of the ICGmicroemulsion to the sebaceous glands in the human skin. The absence offluorescence at the skin surface means that the excess ICG microemulsionwas removed from the skin surface and thus there is no risk of injuringthe epidermis with heat generated in a residual ICG film.

EXAMPLE IV Methods of Clearing Obstructed Pores Prior to ChromophoreAdministration

According to an additional embodiment of the present invention, thesurface of the skin to be treated with the chromophore is cleaned priorto chromophore administration to remove any excess surface oils anddebris which could potentially block the lipophilic absorption of thechromophore into the targeted sebaceous glands. When subjected to thecleaning step, pores which may be either partially or wholly obstructedby buildup of sebum, oil, dirt, cosmetics or other foreign material arepartially or wholly cleared to allow or otherwise improve access of thechromophore to the sebaceous gland. In this manner, delivery of thechromophore to the targeted sebaceous gland is enhanced when compared toadministrations of chromophores where the skin has not been cleaned andthe pores have not been cleared.

According to this aspect of the present invention, a 10 cm×10 cm area ofskin to be treated was wiped with an alcohol swab. A 70% glycolic acidsolution was then applied to the skin surface and then left on for about5 minutes. The glycolic acid solution was then neutralized with GLYTONE®post peel neutralizer available from Genesis Pharmaceutical Inc.(Morristown, N.J.), and the area was dried. Other suitable neutralizingagents include but are not limited to water, sodium bicarbonatesolutions, e.g. 5% sodium bicarbonate, etc. The neutralization processwas performed by wiping the area with water, e.g. using a water-soakedgauze pad, and subsequently applying a liberal amount of the neutralizeron the treated skin area. The treated area was then rinsed liberallywith water. A lipophilic formulation of indocyanine green was thentopically applied to the skin area and covered with an occlusivedressing for 24 hours.

Additional methods for removing excess surface oils and debris from skinand for clearing pores include topical administration of salicylic acidpreparations in the forms of washes, gels or peels; topical retinoicacid therapy; and mechanical processes including microdermabrasion. Thearea of the skin to be cleaned may optionally be heated to promote poreopening and to facilitate better cleaning of the skin area. It is to beunderstood that additional methods for clearing pores which are usefulin the present invention will become apparent to those skilled in theart based upon the present disclosure.

EXAMPLE V Irradiation of Sebaceous Glands Containing SelectivelyIntroduced Chromophore

Irradiation of an area of skin being treated by a method of the presentinvention is accomplished with a laser that emits light energy at awavelength strongly absorbed by the selected chromophore, but largelytransmitted by the outer layers (first 1-2 mm) of the skin. For example,a preferred chromophore, indocyanine green (ICG; also known as cardiogreen) absorbs strongly at 810 nm, a wavelength at which melanin, theprimary human skin pigment, does not absorb strongly. Thus, a laseremitting light at this wavelength is preferred if ICG is used as thechromophore.

The laser radiant energy, or fluence of laser light useful according tothe invention will vary with the absorption coefficient of thechromophore used and may be predicted by a Monte Carlo simulation of thelaser-tissue interaction, or may be determined empirically using anappropriate animal model. In a Monte-Carlo computer simulation, theoccurrence of each of the possible mechanisms for interaction betweenthe laser radiation and the target tissue is assigned a probability. Thepath of a single quantum of laser radiation through the target tissue isthen divided into many small steps. At each step, the overall effect ofthe radiation is determined by chance consistent with the assignedprobabilities. This process is repeated many times until a statisticallyvalid picture of the overall effect is obtained. In a typicalapplication, experimental data are used to determine the probabilityassignments. There is a number of Monte-Carlo simulation packages thatare commercially available. The Monte-Carlo simulation package used hereis derived from the work of L. H. Wang, S. L. Jacques, and L. Q. Zheng,“MCML—Monte Carlo Modeling of Photon Transport in Multi-layeredTissues”, Computer Methods and Programs in Biomedicine 47, 131-146(1995) and L. H. Wang, S. L. Jacques, and L. Q. Zheng, “CONV—Convolutionfor Response to a Finite Diameter Photon Beam Incident on Multi-layeredTissues”, Computer Methods and Programs in Biomedicine 54, 141-150(1997) and is available through the Internet.

The fluence is directly related to laser intensity, and should bemaintained as low as possible to effect thermal disruption of sebaceousglands that have concentrated the chromophore while limiting damage tosurrounding tissues. Optimal fluences range from about 0.1 J/cm² toabout 50 J/cm². For indocyanine green, for example, it is preferred thatthe fluence of the light emitted by the laser is in the range of about 5J/cm² to about 40 J/cm².

It is preferred that the laser be pulsed during the irradiation of thearea being treated. Pulse duration may vary over a range ofapproximately 1 μsec to approximately 500 msec, depending upon the laserused, the chromophore used, and the amount of chromophore selectivelyintroduced to the sebaceous glands. Longer pulses are generally moreeffective for disruption of larger glands that have longer thermalrelaxation times than are short pulses. When using indocyanine green asthe chromophore, for example, the pulse duration should be about 1 toabout 100 msec.

The pulse duration and fluence determine the laser intensity deliveredto the treated area. The intensity should be low enough to minimize theformation of a shockwave that can damage surrounding tissue and tominimize tissue vaporization or explosive tissue ablation.

According to the present invention, the amount of ICG that must beintroduced and the fluence required to damage the sebaceous gland isestimated based upon the estimated temperature rise in the gland at agiven fluence and pulse duration. A temperature rise of 30° C. sustainedfor more than about 10 msec is sufficient to disrupt the gland. Tables Iand II show the results of such estimates obtained by means of a MonteCarlo simulation of the laser:tissue interaction. For this estimate, thegland is assumed to have 5% ICG lipid. The results depend strongly uponthe absorption coefficient of ICG in the lipid chromophore suspension.Experimentally, this coefficient was found to lie between the limitsgiven in the tables (i.e., 350 cm⁻¹ to 690 cm⁻¹).

The expected temperature rise (ΔT) of a gland for the case in whichfluence incident in the tissue is 10 J/cm² and the pulse duration iseither 50 or 20 msec are shown in Tables I and Table II respectively.TABLE I Calculated Temperature Rise Expected within the Sebaceous Glandin ° C. Pulse Duration 50 ms, 10 J/cm² on the skin surface in a 5 mmspot (39W) Gland Diameter Lipid ICG 50 μm 100 μm 200 μm 5% 350 cm⁻¹ 3 1030 5% 690 cm⁻¹ 6 19 55

TABLE II Calculated Temperature Rise Expected in the Sebaceous Gland in° C. Pulse Duration 20 ms, 10 J/cm² on the skin surface in a 5 mm spot(98W) Gland Diameter Lipid ICG 50 μm 100 μm 200 μm 5% 350 cm⁻¹ 5 19 495% 690 cm⁻¹ 10 35 89

The size of the gland has an effect on the expected temperature rise, asseen in the table, with a nearly 10-fold increase in expected ΔT in 200μm glands compared to 50 μm glands at either fluence or pulse durationsetting. It is evident from the table that at 1% lipid solution uptake,and if the absorption coefficient of the lipid chromophore solution isactually closer to the lower limit given, that one would need toincrease the fluence above 10 J/cm² to achieve disruption of the gland.On the other hand, at the upper limits of both the absorptioncoefficient and lipid chromophore uptake, 10 J/cm² suffices to achievedisruption. With a lower pulse, 10 J/cm² may be sufficient to achievedisruption in the larger glands.

Since one experimentally finds approximately 5% of the gland volume isfilled with lipid chromophore solution, the range of 5 J/cm² to 40 J/cm²for fluence and 1 msec to 100 msec for fluence will allow thepractitioner to achieve disruption of a broad range of gland sizes.

Laser energy may be transmitted to the area being treated by, forexample, a commercially available optical fiber. One end of the fiber isaffixed to a laser light source, such as a diode laser that emits lightin a wavelength strongly absorbed by the selected chromophore, and theother end is directed towards the area to be irradiated. The size of theoptical fiber aperture, e.g. the diameter of the spot emitted by theoptical fiber, is selected based upon the size of the area to betreated, with smaller fibers suited to smaller areas and larger fiberssuited to larger areas. The laser itself is connected to a control panelto enable the user to turn the laser on and off and to adjust thefluence and pulse rate of the laser energy.

The laser energy may be applied by scanning the emitting end of theoptical fiber over the area being treated. Scanning is accomplished bymanually moving the optical fiber or the laser itself over the areabeing treated. Alternatively, it is contemplated that the scanning maybe accomplished mechanically by mounting the laser or the emitting endof the optical fiber on a scanning apparatus designed to move at acontrolled rate. In this manner the total laser energy applied to anyone given area may be kept constant. Clearly, this latter approach ismost useful when relatively large areas are to be treated.

While any laser that emits light energy at a wavelength and intensitysufficient to disrupt the function of sebaceous glands that have had achromophore selectively introduced is acceptable for use in the methodsof the invention, a preferred embodiment employs a diode laser andindocyanine green as the chromophore. It is preferred that the diodelaser have a wavelength range of 750 nm to 1100 nm, a pulse durationranging from about 1 to about 100 msec, and a fluence range of about 5J/cm² to about 40 J/cm².

A human volunteer with active acne on the back had a small area treatedwith the ICG microemulsion and the laser. Twenty-four hours after thetreatment a punch biopsy sample was taken from the treated area and itwas processed for histological examination. FIGS. 4A and 4B show theresults of a histological examination. The low power view (FIG. 4A) andthe high power view (FIG. 4B) both show that the folliculosebaceousunits have largely been destroyed with surrounding tissue necrosis.Without wishing to be bound by an scientific theory, a pathologyanalysis revealed that the folliculosebaceous unit at the far left ofFIG. 4A had largely been destroyed with surrounding tissue necrosis. Thepathology analysis further revealed that the folliculosebaceous unit inthe middle of the field in FIG. 4A also was largely destroyed with acuteinflammation and necrosis involving the follicular epithelium. Withoutwishing to be bound by any scientific theory, a pathology analysis underhigh power (FIG. 4B) revealed that the left folliculosebaceous unit hada destroyed follicle and the middle folliculosebaceous unit had acuteinflammatory cells present within follicular epithelium in the middle.

EXAMPLE VI

The effectiveness of treatment in reducing sebum production isdetermined by direct measurement of sebum production following the laserirradiation. Sebum production is measured, for example, using aspecialized sebum-absorbent tape, SEBU-TAPES™ (CuDerm Corp., Dallas,Tex.) and image analysis techniques. SEBU-TAPES™ are white, open celled,microporous, hydrophobic films coated with an adhesive layer thatadheres to the skin surface. As sebum is secreted, it is absorbed by thetape, displacing air in the microcavities. As the microcavities in thetape fill with sebum, the lipid-filled cavities become transparent. Thearea covered by transparent spots per cm² is a convenient andreproducible measure of sebum production (Manuskiatti et al., 1999, J.Amer. Acad. Dermatol. 41: 176-180). In order to observe a change insebum production following treatment with the methods of the invention,one may either measure a treated area and an untreated nearby area onthe same individual, or one may measure sebum production over a standardamount of time (e.g., 10 min to 10 hrs) on the area to be treated bothbefore and after treatment. Sebum production is considered “reduced”according to the invention if it is at least 20%, preferably at least40%, more preferably at least 50%, 60%, 70%, 80% or even greater than orequal to 90% lower relative to sebum production either by untreated skinin a similar location or by the treated area prior to treatment.

An alternative method of measuring sebum production is to examinehematoxylin and eosin-stained sections of punch biopsy tissue fromtreated and untreated areas of the same individual, taking note of thesize and morphology of the sebaceous glands before and after treatment.Altered morphology of sebaceous glands is generally indicative ofsuccessful treatment, since altered gland morphology is associated withreduced sebum production.

The reduction of sebum production accomplished through the inventivemethod results in a reduction in the presence and/or severity of acne.The presence or severity of acne may be quantified according to themethod of Michaelsson et al. (1977, Arch. Determatol. 113: 31-36).Briefly, the number of comedones, papules, pustules and infiltrates inan area to be treated are recorded. Each type of lesion is given aseverity index: 0.5 for comedones, 1 for papules, 2 for pustules and 3for infiltrates. A total score that corresponds to the severity of thedisease is obtained by multiplying the number of each type of lesionwith its severity index and calculating the sum of the various lesions(Sigurdsson et al., 1996, Dermatology 194: 256-260). A decrease in theacne severity score of at least 10% or more, preferably 25% or more, 50%or more, 75% or more up to and including a decrease to the score of zero(i.e., no acne), is indicative of reduced acne severity or presenceaccording to the invention.

EXAMPLE VII

10 treatment sites were chosen on the backs of patients with activeacne. Topical indocyanine green dye in a lipophilic carrier was thenapplied to a 10 cm×10 cm area treatment site and covered with anocclusive dressing for 24 hours. The area was then cleaned with alcoholand treated with laser irradiation with a laser from Cynosure, Inc.(Chelmsford, Mass.). The following laser parameters were used:wavelength of 800 nm, 4 mm spot size, 50 msec pulse duration with apulse fluence of 40 J/cm². Photographs of the treatment area were takenprior to the laser irradiation (FIG. 5A) as well as 10 days (FIG. 5B),10 weeks (FIG. 5C), and 10 months (FIG. 5D) post irradiation. Thephotographs taken 10 days, 10 weeks, and 10 months post treatment showeda significant reduction in the presence of visible acne (see rectangularregions in FIGS. 5B, 5C and 5D).

In addition to the treatment of existing acne, the invention alsoprovides a way to prevent the development of acne. The methodessentially comprises the steps of selectively introducing a chromophoreto sebaceous glands, and then irradiating the sebaceous glands andsurrounding area with laser light of a wavelength that is essentiallytransmitted by the outer layers of human skin and is strongly absorbedby the chromophore. The irradiation is performed at a light fluence andfor a time sufficient to disrupt sebaceous gland function such that thedevelopment of acne is prevented.

It is to be understood that the embodiments of the present inventionwhich have been described are merely illustrative of some of theapplications of the principles of the invention. Numerous modificationsmay be made by those skilled in the art based upon the teachingspresented herein without departing from the true spirit and scope of theinvention.

1-14. (canceled)
 15. A method of treating a patient who has an unwantedskin condition associated with the production of sebum, the methodcomprising: generating, on the patient's skin, a target region havingsubstantially clear pores, wherein generating the target regioncomprises applying an acidic composition to an area of the patient'sskin and heating or mechanically abrading the area; topicallyadministering an exogenous chromophore onto the target region, whereinthe chromophore absorbs laser light having a wavelength between about700 nm to about 1200 nm; and irradiating the target region with laserlight having a wavelength between about 700 nm to about 1200 nm for atime sufficient to inhibit subsequent sebum production.
 16. The methodof claim 15, wherein applying an acidic composition to an area of thepatient's skin comprises topically applying a glycolic acid solution ora salicylic acid preparation to the area.
 17. The method of claim 16,wherein the acidic solution is a blycolic acid solution and the methodfurther comprises the step of neutralizing the glycolic acid solution byadministering at least one neutralizing agent.
 18. The method of claim17, wherein the neutralizing agent is water, a sodium bicarbonatesolution, or GLYTONE®.
 19. The method of claim 15, wherein the glycolicacid solution is a 70% glycolic acid solution.
 20. The method of claim15, further comprising, prior to the step of generating the targetregion, a step of wiping an area of the patient's skin with alcohol,wherein the area subject to wiping is substantially the same as thetarget region.
 21. The method of claim 15, wherein the unwanted skincondition is acne.
 22. The method of claim 15, wherein the chromophoreis a lipophilic chromophore.
 23. The method of claim 22, wherein thelipophilic chromophore is beta-carotene.
 24. The method of claim 15,wherein the chromophore is a dye.
 25. The method of claim 24, whereinthe dye is indocyanine green, Rhodamine B, or cresyl violet.
 26. Themethod of claim 15, wherein the chromophore is combined with alipophilic carrier.
 27. The method of claim 26, wherein the lipophiliccarrier is a liposome.
 28. The method of claim 26, wherein thelipophilic carrier is a lipid suspension.
 29. The method of claim 28,wherein the lipid suspension comprises an oil or a surfactant.
 30. Themethod of claim 29, wherein the oil is a sunflower oil, an olive oil, ora safflower oil.
 31. The method of claim 15, wherein the wavelength isbetween abut 750 nm and about 850 nm.
 32. The method of claim 15,wherein the wavelength is between about 800 nm and about 820 nm.
 33. Themethod of claim 15, wherein irradiating the target region with laserlight comprises irradiating the target region with laser light having apulse duration of about 200 msec.
 34. The method of claim 15, whereinirradiating the target region with laser light comprises irradiating thetarget region with laser light having a pulse duration of about 500msec.